Wikipedia:Reference desk/Archives/Science/2008 February 2

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February 2[edit]

Diet and prescribed drugs[edit]

Questions calling for medical advice are not allowed on the Reference Desk. Please consult your doctor. --Anon, 01:58 UTC, 2008-02-02.

Some prehistory questions[edit]

1) When the Paleo-Indians crossed the Bering land bridge, did they spend generations on the journey or did they cross the bridge and the Canadian glaciers all at once? Is this even knowable?

This could be found out (or may already have been) by radio-carbon dating the skeletons found along the supposed route of travel or by anylyzing the stone tools in order to date them (by comparision to stone tools of know age and orgin). So I would say it is probably "knowable". However, there are some current theories that say the Paleo-Indians came from Europe to the North American continent via canoe along the edge of the massive ice-cap that would have been in the Atlantic Ocean. There is also another that says the first North American inhabitants came via canoe from Russia along the edge of the ice-cap in the Pacific Ocean. Zrs 12 (talk) 01:04, 2 February 2008 (UTC)
This would have taken generations. These people had no intent to move south; they were probably following migrating game herds. Only when population stress occurred (on either the humans or on the herds) would there be a need to migrate further. If one group could cross the land bridge, then it is probable that other groups crossed after them as well. These new migrants would either have to force the current residents to move onward, or be forced to move on themselves. − Twas Now ( talkcontribse-mail ) 02:04, 2 February 2008 (UTC)
For what it's worth, I recall reading that genetic research done on native americans shows three distinct waves that people came from Asia to the Americas in and that these populations were fairly small. — Ƶ§œš¹ [aɪm ˈfɻɛ̃ⁿdˡi] 11:17, 2 February 2008 (UTC)

2) Is it really true that Africa was nearly untouched by the Pleistocene extinctions?

One theory suggests that because humanity arose in Africa, and as fledgling early Hominina were only learning to hunt, the animals of Africa adapted to avoid these primates. When early Homo left Africa, they had acquired a certain degree of hunting skills, and the fauna of other lands did not think to avoid these small little creatures. Why would a 7 tonne mammoth be scared of a 75 kg human? − Twas Now ( talkcontribse-mail ) 02:04, 2 February 2008 (UTC)

3) Are there any theories as to why there are no land mammal predators on the size scale of Tyrannosaurus or Giganotosaurus, but there are predatory whales at least as big as the Mesozoic sea predators?

Vultur (talk) 23:49, 1 February 2008 (UTC)

Well, this isn't specific to predators, but Bergmann's Rule is one explanation. The deep ocean is pretty cold, so larger animals have an advantage in the heat retention department. --Bmk (talk) 15:07, 2 February 2008 (UTC)
Good answers, but on 2)I was asking if the African species were in fact unaffected. Were there megafauna extinctions there? Vultur (talk) 17:33, 3 February 2008 (UTC)
The page List of African megafauna includes several species of megafauna that are marked as extinct, so the answer to 2) seems to be no, Africa was not untouched by pleistocene megafauna extinctions. --Bmk (talk) 15:44, 5 February 2008 (UTC)

Winter[edit]

About how many days long is winter? —Preceding unsigned comment added by 64.119.61.7 (talk) 00:44, 2 February 2008 (UTC)

The winter of 2007-2008 is 90 days long. However, I don't know if this varies from year to year or not. Zrs 12 (talk) 00:58, 2 February 2008 (UTC)
Depends on what you mean by "winter". See Seasons#Reckoning, and that list isn't exhaustive either. --Anonymous, 01:56 UTC, 2008-02-02.

Neurontin and Lyrica[edit]

What is the difference between Neurontin (Gabapentin) and Lyrica (Pregabalin) when used to treat neurogenic/neuropathic pain? ៛ Bielle (talk) 01:04, 2 February 2008 (UTC)

Try searching wikipedia! Perhaps reading the encyclopaedia pages linked above and here, Neurontin, Lyrica, will help. The first paragraphs of each article seem to answer your query at a basic level. --Bmk (talk) 01:42, 2 February 2008 (UTC)
See Neuropathy#Treatment of neuropathic pain. hydnjo talk 01:45, 2 February 2008 (UTC)
Thank you, hydnjo. I hadn't seen that article before. Bmk's insertion of the links into my question, along with the repeat of same in his/her answer, all neatly skewered on that exclamation point, tell me I should have written out the long form of my question, which was, as follows:
Having read the articles Neurontin and Lyrica, I understand that the active mechanisms by which either works in the treatment of neurogenic/neuropathic pain are currently unknown. Is there anyone out there in Science Ref Desk Land who knows of any more recent data that would explain the differences between the drugs when used to treat neurogenic/neuropathic pain? Thank you for your patience. ៛ Bielle (talk) 04:01, 2 February 2008 (UTC)
Sorry - didn't mean to sound patronizing. I would have responded differently had I noticed that you were not an anonymous user! --Bmk (talk) 15:01, 2 February 2008 (UTC)
I am sure Bmk can't have meant that it is acceptable to be patronizing to unregistered users just because they are unregistered. ៛ Bielle (talk) 16:05, 2 February 2008 (UTC)
Naturally not - I merely meant that such a comment would be less likely to be taken as patronizing for an unregistered user, as they are less likely to be aware of the rich informational content of wikipedia. --Bmk (talk) 17:23, 2 February 2008 (UTC)
I thought I could hear the crackle of ice under the surface pressure of a fast-moving body, but it turned out to be the faint sounds of far-off laughter. Excellent recovery, Bmk; Toller Cranston would be proud of you. ៛ Bielle (talk) 18:02, 2 February 2008 (UTC)
Yes, well, perhaps skating is best left as a winter sport. A lesson in manners has been suitably delivered. --Bmk (talk) 15:46, 5 February 2008 (UTC)

Speed of gravity[edit]

Has anyone conclusively determined the speed at which the gravitational effect travels?--TreeSmiler (talk) 01:53, 2 February 2008 (UTC)

I assume, if gravity is the effect due to the curving of space by mass (as theorized by Einstein), then gravity would not "travel". It would take effect from any distance instantly. If gravity is indeed carried by "gravitons" as quantum mechanics has hypothesized, then the effect would probably travel at the speed of light, as gravity has an infinite range and therefore its paticles must be massless. However, I am not sure of this and am just trying to put together things I have heard; so if I am wrong, someone please correct me. Zrs 12 (talk) 02:10, 2 February 2008 (UTC)
See Speed of gravity. hydnjo talk 02:15, 2 February 2008 (UTC)
That is, at exactly the speed of light. This has been experimentally verified. 70.162.25.53 (talk) 02:52, 2 February 2008 (UTC)
So would that mean Einstein was wrong about the curving of space by mass? If not, how would curvature "travel" at any speed? Zrs 12 (talk) 03:00, 2 February 2008 (UTC)
Negative. It'd mean Einstein was right - speed of gravity would be an issue of how quickly changes in mass positions propagate. Indeed, Special Relativity demands that in general, information can only travel at most at the speed of light - instantaneous gravity would cause all sorts of simultaneity-related contradictions.--Fangz (talk) 03:18, 2 February 2008 (UTC)
Indeed. As our speed of gravity article says: "General relativity predicts that gravitational radiation should exist and propagate as a wave at the speed of light". And this is entirely consistent with the existence of massless gravitons, which are hypothesised by the various competing theories of quantum gravity. Gandalf61 (talk) 09:23, 2 February 2008 (UTC)
I see. The speed of gravity in the theory of general relavtivity is the speed at which the new curve of space due to a change in mass travels away from the body. Right? Zrs 12 (talk) 15:27, 2 February 2008 (UTC)
Yes. The speed of gravity is the speed at which changes in the gravitational field propogate, and the gravitational field determines the curvature of spacetime. Gandalf61 (talk) 17:07, 2 February 2008 (UTC)

Sky[edit]

Figure showing the more intense scattering of blue light by the atmosphere relative to red light.

Why is the sky blue? 143.43.29.48 (talk) 02:25, 2 February 2008 (UTC)

Rayleigh scattering of sunlight leading to diffuse sky radiation. Rockpocket 02:33, 2 February 2008 (UTC)
I've also gotten that far, but why does air scatter blue light more than the other wavelengths? --Sean 17:50, 2 February 2008 (UTC)
Hmm, maybe the oxygen atoms in the air scatter more blue than all the other colours scattered elsewhere during a clear day? Thanks. ~AH1(TCU) 18:26, 2 February 2008 (UTC)
When Rayleigh scattering of light occurs, the particles doing the scattering (in the air) are smaller than the wavelength of the light being scattered. Because of this, the wavelength of the light becomes a huge factor in determining how much scattering occurs. (Think about it like this: light with a large wavelength has a better chance of "dodging" the small particle than light with a smaller wavelength. Specifically the scattering varies as an inverse of the fourth power of the wavelength. Therefore the smaller the wavelength, the more is scattered.) As the figure to the right shows, blue light is at the short wavelength end of the visible spectrum, therefore it is more strongly scattered in the atmosphere than long wavelength red light. This is why the sky typically looks blue. Rockpocket 22:49, 2 February 2008 (UTC)
Rayleigh scattering doesn't explain all of why the sky is blue -- if it was the only phenomenon involved, the sky would be purple. The reason why the sky is blue is that human eyes are far more sensitive to cyan and blue than to purple. --Carnildo (talk) 02:55, 3 February 2008 (UTC)

Getting back into a normal sleep pattern, ideas?[edit]

Im not sure about your various countries but here in my country we get about 7 weeks off from school over christmas and into janurary. Almost every day ive been going to bed at 4am and waking up at 2pm. Now today is saturday and i start monday and i ususally wake up at 7:30ish any ideas to help me snap back into my normal sleep pattern. Someone suggested that i dont sleep tonight, so it will be easier for me to sleep tomorrow, wonder if this will work..hmm. Anyway any ideas? =] . —Preceding unsigned comment added by 121.219.227.98 (talk) 06:46, 2 February 2008 (UTC)

That’s the kind of metaturnal sleep schedule I too engage in when given the opportunity. :) If you had a week to do it there is a less painful way, but if you have to be at school on Monday staying awake all night may be your only option. (Don’t plan anything big for tomorrow.) Alternatively you could just go to school with only three hours of sleep. --S.dedalus (talk) 07:29, 2 February 2008 (UTC)

Yeah it does but you will sleep longer than normal. Plan for 12+ hours sleep on Sunday night —Preceding unsigned comment added by Shniken1 (talkcontribs) 13:05, 2 February 2008 (UTC)

Hi. Not sleeping for a whole night is a pretty bad idea, which is why I've never done it, ever. Sleep is nessecary because the body needs rest, and it also helps regulate growth, which is why teenagers and children need more sleep than adults. Fluctuating your sleep patterns in a short period of time is not very good either, and in extreme cases you may suffer from sleep irreglarities similar to that of jet lag. However, I've read that Inuits often get six hours of sleep in summer, and fourteen in winter, but that's over a long period of time and I assume they're not on a very tight schedule. I've also heard of people who sleep and wake 40 minutes later each day than the previous one, in order to keep up with the Martian sol so they cn track the rovers. Whatever you do, please use common sense as getting a lack of sleep on your first day of school can cause you to become very tired and lose concentration, especially if you have a test, but usually they don't give you a big test on the first day of school after a long time of holiday. Anyway, I guess you're pretty lucky to have 7 weeks of holidays in winter, where I live the December-January and summer vacation combined only total about 12 weeks. Hope this helps. Thanks. ~AH1(TCU) 18:40, 2 February 2008 (UTC)
AstroHurricane, have you ever worked shifts? Skipping a sleep period is a pretty standard way of moving to a different sleep pattern, and works much quicker than just about any other method. Getting into a new sleep pattern quickly results in less sleep lost overall, in these circumstances. Ideally, you are right, sleep patterns should not be fluctuated in this manner, but sometimes they have to be. The person asking the question needs to shift their sleep pattern about 6 hours by tomorrow, and any way of doing that is going to involve missing out on sleep and being tired; the quickest way that mucks you up least is to miss a night's sleep so that you will fall asleep at the right time to get enough sleep to awaken refreshed the next day. If you have a week or so to get back into the normal pattern, that is obviously better, but they don't. Skittle (talk) 14:06, 3 February 2008 (UTC)

He never mentioned it was winter. —Preceding unsigned comment added by Shniken1 (talkcontribs) 05:51, 3 February 2008 (UTC)

“To stay awake all night adds another day to your life.” Stilgar, Dune --S.dedalus (talk) 23:09, 3 February 2008 (UTC)

Lava lake in Krakatau?[edit]

Google maps image of the volcano with an orange/red spot in the caldera. (Not unlike this image of Mt. Erebus.) I've seen news about its recent activity but nothing mentioned a persistent lake. Anynobody 09:37, 2 February 2008 (UTC)

Hi. I'm not sure about the lake in particular, but I'm noticing something very unusual about the image. Between the orange spot and the southern part of the island that appears to be shrouded in smoke, is a bluish smoky reigon on the west flank of the volcano. If you look closely you can read the bluish-grey numbers "2008" on that area. Were these images taken this year? Is this true for the other reigons as well? Have they updateded Google Earth with new images? Thanks. ~AH1(TCU) 18:46, 2 February 2008 (UTC)
It looks like 2006 to me. Saudade7 20:46, 2 February 2008 (UTC)
Anyway, the year on a copyright notice is not necessarily the year the photo was taken. They could be claiming copyright on the specific version of it that you're seeing (whether that's valid or not, which would be a legal question and not appropriate here). It's certainly true that Google Maps/Earth images may be a few years old; I've seen that by looking at images of places near where I live, where there have been changes I can look for. --Anonymous, 23:22 UTC, 2008-02-02.

Thank you for the replies, I can't speak for everywhere Google Maps updates their info, however where I live seems to be updated regularly. (I suspect large urban areas are most often updated. As to the image of Krakatau, it probably is from 2006, and Google probably updates images by area since this is from 2007/8 and the Google copyright doesn't appear anywhere (which to me indicates that they phased out the watermark after the image in my first link was taken and that area hasn't been updated for a while).

The Krakatau image looks like it was taken in either the morning/evening or has somehow been corrupted given how dark it is. The weird color overall is what makes me somewhat second guess it being lava. Anynobody 07:03, 3 February 2008 (UTC)

Antimatter[edit]

I've heard about antimatter but I don't know what it is (please use short words!). 86.0.85.244 (talk) 09:45, 2 February 2008 (UTC)

It is the same thing as matter, except that the electrons have positive charge, and the protons have negative charge. Positively charged electrons are called positrons, and negatively charged protons are called antiprotons. It is also my understanding that neutrons are replaced by antineutrons, see Antimatter#Antiuniverse. Check out the antimatter article for more details. --NorwegianBlue talk 10:49, 2 February 2008 (UTC)
That's correct as far as it goes, but we can add another level of detail. The difference between a particle and its antiparticle is not just a change of sign in their charge, otherwise every neutral particle, such as a neutron, would be its own antiparticle. Leptons such as the electron and the neutrino have a lepton number of 1; their antiparticles have a lepton number of -1. Baryons such as the proton and the neutron have a baryon number of 1; their antiparticles have a baryon number of -1 (in fact, the situation with baryons is a little more complicated, as they actually consist of fundamental particles called quarks, which have antiparticles called antiquarks). Lepton number and baryon number are two types of quantum numbers. Particles which have a lepton number of 0 and a baryon number of 0 are their own antiparticles - these include photons and particles such as the neutral pion which are a bound state of a quark and its antiquark. Gandalf61 (talk) 12:07, 2 February 2008 (UTC)
We have an article about antimatter at the Simple English Wikipedia. (EhJJ) 12:20, 2 February 2008 (UTC)

Insect in a vacutainer?[edit]

What would happen were i to put an instect or a spider, say, in a vacutainer with the different chemicals in side them? E.g. clot accelerator, lithium heparin, Potassium EDTA, sodium citrate, etc? Otehr than maybe die, but would it like.. dissolve, etc?

Regards. —Preceding unsigned comment added by 79.67.251.46 (talk) 14:57, 2 February 2008 (UTC)

You mean letting the air enter the vacutainer first, then putting the arthropod inside? Yes, it would die, eventually. No, it won't dissolve. Chitin-protein exoskeleton of an arthropod is quite hard to dissolve. Why do you expect anticoagulants (heparin or citrate) to dissolve an arthropod?! If the cuticula is broken in any place, some haemolymph would leak out (maybe more than usually because of the anticoagulant), but that's it. So no, the arthropod won't dissolve. Actually, I'm not even sure heparin has any effect at all in arthropods, or any invertebrates for that matter. Haemolymph is quite different from mammalian blood. --Dr Dima (talk) 15:31, 2 February 2008 (UTC)

monoclonal antibodies[edit]

why are only mice used in production of monoclonal antibodies? or are any other animals being used for the same and why?

Have you read Monoclonal antibody ? --Dr Dima (talk) 15:37, 2 February 2008 (UTC)
There are some rat-derived monoclonal antibodies available from the Developmental Studies Hybridoma Bank. I haven't read the papers that describe the generation of the antibody (see rat anti-Elav). Perhaps they have more detail on what is involved. And I'm not sure why mice are the predominant species used. -- Flyguy649 talk 20:22, 4 February 2008 (UTC)

smell of eggs and farts[edit]

what is it that gives certain types of farts and eggs their pleasant odour? a certain chemical maybe?--Sonjaaa (talk) 15:56, 2 February 2008 (UTC)

Hydrogen sulfide.--The Fat Man Who Never Came Back (talk) 16:00, 2 February 2008 (UTC)
To (hopefully) add something to the discussion here, compounds or reactions with sulfur are often smelly. I've been told that's why your hair can smell during/after a perm. --M1ss1ontomars2k4 (talk) 01:14, 8 February 2008 (UTC)

Plants[edit]

If the leaves of a plant didn't lose water through diffusion, the water taken in by its roots wouldn't be able to travel up the plant because of the low gradient. Would it die? xxx User:Hyper Girl 16:05, 2 February 2008 (UTC)

Plant leaves are never completely watertight, but a cactus, for example, loses very little water. Like a cactus, your plant would simply stop taking up water once it held as much as it could. This is an example of homeostasis. The plant wouldn't die because it still has water inside it, and could always draw some up more from the roots when needed. Think outside the box 16:17, 2 February 2008 (UTC)
The water does not only travel up the stem of the plant, it also travels down. So no, the movement of fluid in the plant would not necessarily cease. Not all plants are capable to survive even the temporary loss of leaves; but the defoliated plant dies not (or not only) because of the slow-down of nutrient transport from the root. So let's assume the leaves are still there. I do not know if it is possible to block water emission through leaves but not to block photosynthesis and respiration. Perhaps, simply raising humidity to 100% would work for some plants; others will "bleed" excess water through the leaf pores. It mostly depends on the ambient temperature if 100% humidity would kill a plant or not: if it's hot, death will occur quite fast due to overheating. If it's not too hot, death may, indeed, occur (much slower) due to excessive water intake and/or chemical imbalance. To summarize, I think the answer is "it depends on the choice of plant, the choice of environment conditions, and the choice of the way to block water emission". Hope this helps. --Dr Dima (talk) 17:16, 2 February 2008 (UTC)

What is Gravity?[edit]

I have asked around, and no one can give me a straight answer. Some people say it's a force, some some say it's an acceleration and I'm completely confused. Help! KarateKid101 (talk) 16:36, 2 February 2008 (UTC)

it's a force that causes things to accelerate.87.102.44.109 (talk) 17:07, 2 February 2008 (UTC)
A common confusion is defining what is meant by the word "gravity." Are you referring to the "effect of gravity" or the "cause of gravity?" The effect of gravity is a force that causes mass to be naturally attracted to other particles of mass. The cause of gravity is unknown. -- kainaw 17:38, 2 February 2008 (UTC)
You'll never get a straight answer to this question for the same reason you'll never get a straight answer to "what is multiplication?" or "what is a chair?". The only way to understand what something is is to work with it for a while until you get an intuition for its behavior. We can tell you things about gravity, but there are a lot of things one can say about gravity and everyone will tell you something different. There's probably an answer that would enlighten you, but without knowing the nature of your current understanding it's very hard to guess what that answer might be. — BenRG (talk) 19:21, 2 February 2008 (UTC)
Here's a quote from our Forces article: "The definition of force is sometimes regarded as problematic, since it must either ultimately be referred to our intuitive understanding of our direct perceptions, or be defined implicitly through a set of self-consistent mathematical formulae." I guess one could argue, based on general relativity, that gravity is special and might present conceptual problems that the other forces don't... but I get the impression, without knowing enough about physics or philosophy, that most philosophers of science feel that all forces present similar challenges to our ideas about explanation. But the original questioner seemed to be confused about force vs. acceleration, so hopefully 87.102.44.109 cleared that up. Sometimes people refer to "g" (as in 9.8m/s^2) as "gravity", but that's simply wrong. --Allen (talk) 20:10, 2 February 2008 (UTC)
It's a force. However, gravity can be replicated by acceleration. For example, if one were standing in something accelerating at 1g (9.8 m/s^2), that would be equivelent to standing on earth. Gravity is also a cause of acceleration. As far as the cause of gravity: It is described as virtual particles (gravitons) by quantum physics and as the curving of spacetime by matter in the relativity theory. Zrs 12 (talk) 00:26, 3 February 2008 (UTC)
Well, moving it a little further, it's not just "replicated", it's at times indistinguishable. That distinction meant a lot to Einstein—he's not concerned with which effect is "really" gravity or not! --24.147.69.31 (talk) 16:38, 3 February 2008 (UTC)
It all depends which model of gravity you are using. In Newtonian gravity, gravity is a force at a distance, which causes objects to accelerate, unless it is opposed by an equal and opposite force (typically because an object is standing on something). However, Einstein's theory of general relativity does away with the "force at a distance" idea, and says that gravity is just another word for the curvature of spacetime, and an object on which no forces are acting will follow a geodesic in spacetime (commonly described as being in free-fall).
To see the difference, consider person A standing on a cliff, and person B who has just jumped off the cliff and is in free-fall. Newton says that person A is in equilibrium because the downward pull of gravity is balanced by an upward normal force from the ground, and person B is accelerated downwards with respect to person A by the unbalanced force of gravity. Einstein says that person B, in free-fall, has no forces acting on them, and is therefore in equilibrium, and person A is accelerated upwards with respect to person B by the unbalanced normal force from the ground.
In almost all circumstances the two models give identical results. In the few cases where they give different results (bending of light; precession of the orbit of Mercury), experiments have proved that general relativity is the more correct model. Gandalf61 (talk) 11:12, 4 February 2008 (UTC)
Gandalf, in your scenario with the people on the cliffs, couldn't the general relativity point of view be either? Couldn't either person B or person A be considered to be accelerating? Zrs 12 (talk) 20:49, 4 February 2008 (UTC)
Yes, acceleration is relative, so you can regard either person as accelerating relative to the other, or indeed you can regard both as accelerating relative to some other frame of reference. The important point is that in general relativity there are no forces acting on the free-falling person B - there is no "force of gravity" in general relativity. Gandalf61 (talk) 10:48, 5 February 2008 (UTC)

Diet question[edit]

This is an academic question and does not seek medical advice. Does eating a diet high in saturated fats completely or only partially negate the positive effects of statins? —Preceding unsigned comment added by TreeSmiler (talkcontribs) 17:16, 2 February 2008 (UTC)

I assume you understand that statins work by blocking the cholesterol-producing enzyme in the liver. Depending on the dose, statins can block up to 60% of cholesterol production. If a person did not change his or her diet, total LDL cholesterol would still decrease because the liver would produce less cholesterol. Statins also change the ratio of LDL to HDL. A higher percentage of HDL is beneficial. All in all, reducing cholesterol intake will provide a benefit of lowered total cholesterol. Statins will reduce LDL further and increase the HDL ratio. -- kainaw 17:36, 2 February 2008 (UTC)
no I didnt know that. And thank you. That all I wanted to know.--TreeSmiler (talk) 17:39, 2 February 2008 (UTC)

Compact fluorescent lamps and flicker?[edit]

From the article of CFLs: "Integrated lamps combine a tube, an electronic ballast and either a screw or bayonet fitting in a single CFL unit. These lamps allow consumers to easily replace Incandescent lamps with CFLs." From the article on electronic ballasts: "Electronic ballasts usually change the frequency of the power from the standard mains (e.g., 60 Hz in U.S.) frequency to 20,000 Hz or higher, substantially eliminating the stroboscopic effect of flicker (100 or 120 Hz, twice the line frequency) associated with fluorescent lighting (see photosensitive epilepsy)."

Is in then a safe bet to assume that CFLs simply do not flicker? Or, rather, flicker at an insanely high rate that simply cannot cause problems (headaches, seizures etc)? Or, is it only safe to assume that most do not cause problems? The bulbs in question are IKEA GA607 11W bulbs, but I doubt anyone knows the answer for that very model. ;) Aeluwas (talk) 18:33, 2 February 2008 (UTC)

Huh. Found this: "I have run a series of measurements on various electronically ballasted CFLs and found substantial amounts of 120 Hz flicker; typically 1/3 to 1/4 as much as found in linear lamps operated at 60 Hz on EM ballasts." link Aeluwas (talk) 18:54, 2 February 2008 (UTC)
I found that Compact fluorescent lamp caused interference on my infra red link headphones. I stopped using the headphones.--TreeSmiler (talk) 01:41, 3 February 2008 (UTC)
There are individual differences in the ability to see flicker. Some individuals have rejected CFLs on the ground that the flicker they see causes headaches. Temple Grandin has said that some autistic persons have a higher sensitivity to flicker than neurotypical individuals. If the electronic ballast in fact ran the fluorescent bulb at 20,000 Hertz, no one would see any flicker. 60 Hertz flicker might be perceptible to some people. Incandescent bulbs do not turn off completely during each AC cycle, because the filament cannot cool off that fast. Lower power incandescent bulbs have less thermal inertia and should show more flicker. Fluorescent bulbs are able to go on and off more completely during the low voltage part of each cycle. Edison (talk) 02:04, 3 February 2008 (UTC)
we have an article on this Flicker_fusion_threshold--TreeSmiler (talk) 02:17, 3 February 2008 (UTC)
If a CFL is placed in a receptacle with a triac dimmer, it may function strangely, causing flickering. Ilikefood (talk) 22:10, 6 February 2008 (UTC)
Low-quality CFLs may flicker, dimmed CFLs may flicker, and old CFLs may flicker. --M1ss1ontomars2k4 (talk) 01:17, 8 February 2008 (UTC)

how inefficient are wall warts?[edit]

I've read about how wall warts draw power whenever they're plugged in, but how much power? Does my 60W MacBook wart always dissipate 60W minus whatever is being used by the computer? If not, how does the power dissipated by the wart relate to the power used by the device? Thanks. --Allen (talk) 19:48, 2 February 2008 (UTC)

  • I am not sure about the Wall Warts, but I did hear, maybe on a recent "This Week in Science" podcast, that literally half our energy consumption is for things that are plugged in but not being used..things on "stand-by" so I imagine that the Wall Wart is also just drawing energy all the time whether the device connected to it needs energy or not. On that Wall Wart page it just says that 4% of energy use is attributed to such devices, but that is rather vague. Saudade7 20:43, 2 February 2008 (UTC)
    • I would expect a wall wart to draw substantially less than rated power when it is idling. That said, there was a time when "off" meant "off" for TVs and other appliances, with a single pole, single throw switch which killed all power flow. The multitide of plug in adapters are power vampires which draw some small amount of electricity 24/7 and have a very poor power factor. With a wattmeter you could measure the draw when the appliance is on versus off. If the appliance has a battery in it, like a laptop computer, then the idling draw should be greater than if the adapter is for an appliance which is switched off in the old-fashioned sense. A transformer has an "exciting current" which flows even if no power is drawn out of it.Edison (talk) 01:55, 3 February 2008 (UTC)
It depends on the type of transformer. A simple step-down transformer with a rectifier and some filtering capacitors will draw a lot of power no matter what. Your MacBook, on the other hand, probably has a switch-mode power supply, which draws almost no power when the computer doesn't need it. --Carnildo (talk) 03:05, 3 February 2008 (UTC)
Why? And what kind of standby power load were you talking about when you said "a lot"? --72.94.50.76 (talk) 23:35, 3 February 2008 (UTC)
Yeah. A transformer with an open secondary will draw no current from the mains, and that is what we have when no load is connected to the output of the simple transformer/diode/cap power supply. --Milkbreath (talk) 12:40, 4 February 2008 (UTC)
With wall warts, it is usually easy to check. Put your hand on it. If it is warm, it is sucking juice. When I lived in a colder part of the country, I kept all of mine on a power strip under my desk and used them for a foot warmer while working at my computer. As for Sudade7's comment about power consumption, I cut my monthly electricity bill from around $120/month to $80/month by putting all of my electronics on power strips and turning off the power strips when the electronics were not in use. A coworker believes that completely cutting power to them will cause them to break faster - meaning I'll lose money in the long run, but he has no reason for his belief. -- kainaw 13:44, 4 February 2008 (UTC)
"...but he has no reason for his belief." A thought experiment: Have you ever seen a regular incandescent light bulb fail "in use"? That is very rare. Instead, they almost always fail during startup or shutdown, when there is a rapid change in temperature of one part (the filament) followed by a much slower change in temperature of another part (the glass base). They fail BECAUSE of the rapid change in temperature.
OR: Before I was born, my daddy's daddy dammed the stream behind his house, installed a waterwheel, hooked it up to an old card generator, did something unnatural to the voltage regulator, and ran the entire back yard's lights from it. Yeah, the light was kinda orangish due to the low voltage, but it was free power. Those lights were never turned off, and they never burned out. Your coworker has very good reason for his belief. Make an economic decision: Is it cheaper to pay to keep the stuff running, consuming power, or is it cheaper to replace the stuff when it breaks due to the on/off cycle? For many things, the cost in money, time, and aggravation of replacement is great enough that you just leave them running.
Also, compare with the modern (FSVO) "instant-on" CRT TV. TVs used to need several seconds to start up, because the High Voltage Power Supply (HVPS) had to charge up the CRT. Then, manufacturers realized that, if you kept the HVPS up all the time, but turned off the tuner, amps, and gun, the TV would start up very quickly, and people would buy that. Such TVs also lasted much longer, since they didn't have the same thermal cycle as the older ones. Of course, they used much more energy than the older ones.... -SandyJax (talk) 20:28, 4 February 2008 (UTC)
This argument is valid, but misleading. We are discussing having equipment fail in something around 10 years instead of 15 years. Without putting it in a time frame, it is making it sound as if turning off your computer will cause it to fail in a matter of days (which is what my coworker claimed). I've had one television since 1993 and the other since 1995. I've had the same VCR since 1995 (I bought it with the TV). I got my receiver, CD player, radio, and speakers in 1994. The speakers molded when the ceiling leaked on them - but the rest of the system still works fine. I've had the same two monitors on my computer since 1998. I buy a new computer every September, so it is never more than a year old. I got my printer in 1995, but it was used, so I don't know how old it is. All in all, completely powering down my electronics when I'm not using them (which can be for many days or even weeks) hasn't caused any of them to suddenly fail. My car, on the other hand, always broke when I was gone for long periods of time. Leaving it sit for longer than a week would guarantee that something would break. -- kainaw 23:48, 4 February 2008 (UTC)

Teeth Whitening Strips[edit]

We are working on a multi-disciplinary experiment in chemistry/biology involving teeth whitening strips.

Each group used a different type of strips: Crest Classic, Listerine Dissolving, and Equate (Wal-Mart Brand). The active ingredients in all of these is hydrogen peroxide.

Could someone please help explain the science of how this works? Also, does anyone know the percent hydrogen peroxide in any of these strips or how to find this information? Any other additional information would be helpful also. —Preceding unsigned comment added by Kuanche (talkcontribs) 19:53, 2 February 2008 (UTC)

Hydrogen peroxide is an oxidiser, and works the same way bleach does to cloths. --antilivedT | C | G 21:32, 2 February 2008 (UTC)
This section gives more detail about how bleaching works.--The Fat Man Who Never Came Back (talk) 16:34, 3 February 2008 (UTC)

ethylene[edit]

Does temperature affect the amount of ethylene produced from a fruit? —Preceding unsigned comment added by 70.79.131.252 (talk) 19:54, 2 February 2008 (UTC)

Yes. Higher temperature, more ethylene. [1]. --Allen (talk) 20:13, 2 February 2008 (UTC)

PHYSICS MAGAZINE QUESTION ABOUT AN ELEVATOR[edit]

Hey, it`s Me The Physics Magazine Guy I have this thing Here where two elevators are heading to the first floor of an office building. A scale is on the floor and a student is stepping on it. Another,is recording the speed as it moves up the elevator at rest. The elevator,goes up to the fifth floor. What,is the weight of the scale as it moves upward. The weight,the scale shows as velocity of the elevator becomes constant. The weight the scale shows as elevator slows down to a stop. The time the elevator took to make a trip from the 1st to the 5th floor. —Preceding unsigned comment added by 68.161.50.113 (talk) 19:57, 2 February 2008 (UTC)

You don't have enough information. -mattbuck 00:37, 3 February 2008 (UTC)
If the student weighed 150 pounds and the elevator took a very long time to go to the 5th floor, the scale would show 150 pounds. If it accelerated very swiftly, the scale might show 300 pounds or more. When it decelerated as it approached the target floor, it would show less than 150 pounds, even zero or negative pounds if the elevator were badly out of order, the scale was bolted to the elevator, and the student was strapped to the scale! Force equals mass times acceleration, in addition to the weight due to gravitational attraction. Your question is like asking what color the carpet in the hall was. Not enough information. Edison (talk) 01:49, 3 February 2008 (UTC)
The carpet in the hall was red. It always is in these places. -mattbuck 21:34, 4 February 2008 (UTC)
To be frank, I don't think we even have enough information to determine what the question is asking. --M1ss1ontomars2k4 (talk) 01:23, 8 February 2008 (UTC)

Black Butterflies South American Plateau Fields of Crystals Art Bell...[edit]

I once heard an interview on Art Bell's late-night radio show Coast to Coast am. The guest was a man who was an explorer who was going to have a special on Discovery channel or History channel or another similar cable channel. He and his team had gone to some high mesa or butte or plateau in South America - maybe Peru or Brazil - to explore an area that was so geographically isolated from other ecosystems that the animals and plants there had evolved very differently. There were fields of white crystals and black rocks and butterflies were black as were various reptiles...maybe he even said there were black plants (???).

I think there was also a woman biologist in the expedition who worked on extremeophiles that lived in caves. She discovered that the stalactites in a cave there was actually some kind of colony - like a coral reef - of microorganisms that derived their nutrients from calcium-rich water seeping through the rock...something like that.

This has been driving me crazy for a long time. I have looked through all the "Coast to Coast am" past shows but none of the abstracts sound familiar. I feel like it was around summer of 06, but I am not sure. I have even Googled key words to no avail, but I do remember that right after the show aired there was a video from the show on the History Channel or Discovery Channel website so It really was a real expedition and not just a crazy person on Art Bell.

Any ideas of the explorers / scientists / place etc? Thanks Saudade7 20:36, 2 February 2008 (UTC)

Sounds like the table top mountains of Venezuela. Check out our article Tepui.--Eriastrum (talk) 21:05, 2 February 2008 (UTC)

Oh! I am sure that has to be it!!! Thanks Eriastrum!!! Saudade7 05:07, 3 February 2008 (UTC)

Stone dropping falcon[edit]

While sailing we noticed a bird of prey - I believe a falcon - inspecting the boat from quite close. It stayed with us for about 5 minutes and before flying off dropped a 5 cm stone on us. What kind of behaviour would that be? Do Falcons take stones with them as ballast or as a tool for helping with balance. Or are they using it to stun a prey or test the objects or animals they encounter? Any suggestion welcome. Keria (talk) 21:57, 2 February 2008 (UTC)

I don't know about falcons dropping stones, but it is possible that the bird was a gull. They often will drop clams or other hardshelled animals on hard surfaces in order to break them open. They will sometimes drop stones by mistake.--Eriastrum (talk) 23:09, 2 February 2008 (UTC)
I'm not sure I know about any marine falcons. Ospreys catch fish; gulls and crows often drop hard food objects to break them. I tend to agree with Eriastrum. It may have been a gull. Bckirkup (talk) 23:23, 2 February 2008 (UTC)
Sea eagle. --S.dedalus (talk) 02:55, 3 February 2008 (UTC)
Not a falcon... (Accipitridae, not Falconidae)Bckirkup (talk) 15:56, 4 February 2008 (UTC)
Good point. It is a bird of prey however. Looks like the OP has positively identified the bird though. --S.dedalus (talk) 01:39, 5 February 2008 (UTC)
This is interesting, but to be clear it was most definitely a raptor or bird of prey and not a gull. We sailed out of Freetown in Sierra Leone. These huge birds circle all day above the town. There are a lot of white belied crow like birds there too but this was much bigger than a crow and black with a short beak and with those long fretting feather at the tip of the wings. The mistaken clam idea sounds good though. Thank you. Keria (talk) 01:12, 3 February 2008 (UTC)
One is reminded of the unusual death of Aeschylus, killed when an eagle dropped a live tortoise on his (bald) head. The tortoise lived; Aeschylus - alas - not so much. - Nunh-huh 01:55, 3 February 2008 (UTC)
Check out our article Black Kite. Could this be the bird that you saw, behaving in a gull-like fashion?--Eriastrum (talk) 16:27, 3 February 2008 (UTC)
Not only does it look exactly like what I remember of it - especially the wide wings and seperated long feather all along their ends - but the description of behaviour and localisation in the article matche exactly what I could observe. Thank you very much Eriastrum and everybody else for the help. Keria (talk) 17:26, 3 February 2008 (UTC)

Tasting heat[edit]

I believe when breath starts forming into white condensation when exhaling it indicates temperatures of 8ºC and under (maybe varying with humidity in the air?). Is there an equivalent for high temperatures such as feeling the heat on ones palate or tong? Keria (talk) 22:01, 2 February 2008 (UTC)

Well the eight degree temperature that you quote, is being measured from a physical phenomenon, and has nothing to do with sensory perception from the mouth, so I don't understand your assumption of an "equivalent". If you put something in your mouth that's too hot, you notice, so you obviously have the ability to sense temperature via the mucosal tissues in your mouth. If you put something in your mouth at 8 degrees, you'll most likely notice that it's colder than an object of similar composition at 20 degrees. Likewise, you'll notice a difference between something at 39 degrees compared with 60 degrees - there's no special single temperature that could be deemed in any way "equivalent" to the temperature at which moisture in exhaled breath condenses. ----Seans Potato Business 23:43, 2 February 2008 (UTC)
Ah ok, let's make it this then: What ways are there to estimate the temperature in hot climates without the use of a thermometer? Keria (talk) 01:15, 3 February 2008 (UTC)
If you can fry eggs on your belly, its hot!--TreeSmiler (talk) 01:48, 3 February 2008 (UTC)
Bimetalic strips? You could have several configured for indicating different temperatures... maybe you'd only need one and can calibrate it against a real thermometer so that the temperature reading is given by the degree of bending. ----Seans Potato Business 02:07, 3 February 2008 (UTC)
Oh, apparently that might count as a thermometer... does it have to be sensed with your body? Just touch it and guestimate? --Seans Potato Business 02:10, 3 February 2008 (UTC)
If wind feels warmer than still air then the temperature is definitely above body temperature. The neutral point were wind feels like the same temperature as still air should be slightly above body temperature because at body temperature it still cools by lowering the air humidity in the immediate vicinity of the body and thus increases evaporative cooling. Icek (talk) 01:37, 6 February 2008 (UTC)

Ants on the dole[edit]

An entomologist friend told me that amongst ants and bees there where individuals who wouldn't fit their usual caricature as diligent working insects but would do nothing to help the colony and profit of the work of others. Is this true and has it been studied? Keria (talk) 22:04, 2 February 2008 (UTC)

There are several kinds of phenomena that fit the general description you suggest. Noe and Hammerstein discuss the general phenomena in their article "Biological Markets" Trends in Ecology & Evolution; Volume 10, Issue 8, August 1995, Pages 336-339.
Among ants there are various forms of social parasitism and "cheating." In ant-plant symbioses there ants who "cheat" the plants. Studies are numerous. Perhaps start with Itino et al, Ecological Research; Volume 16, Number 4; December, 2001. It studies part of the problem.
Social parasitism describes certain species of ant that profit from others (somewhat like birds that use other birds to incubate their eggs; like the cuckoo - as opposed to nest stealing, like grosbeaks). I recommend Annual Review of Entomology 2001, Vol. 46: 573-599 - Lenoir et al, "Chemical Ecology and Social Parasitism in Ants" to get some detail as to how this works.
Some ant colonies may contain lazy workers - but this is a problem for the colony. Mo re often the problem is not laziness but illicit egg-laying. There are ways that ants (and bees or wasps) deal with such problems in the colony. You might read D'Ettorre 2004 (Proceedings of the Royal Society of London B) to learn about this.
People are starting, perhaps, to move away from studying such pairwise interactions as a mutualism with cheaters, which will make the whole topic more complex. Try Stanton, 2003 (American Naturalist vol. 162, no4, pp. S10-S23) for a review of this change. Bckirkup (talk) 23:19, 2 February 2008 (UTC)
Are there any instances where individual ants in a colony just "pretend to work"? 71.196.233.110 (talk) 18:02, 3 February 2008 (UTC)
Not sure. If so, they may be editing wikipedia on the sly. Bckirkup (talk) 15:57, 4 February 2008 (UTC)

Speed of waves[edit]

I think waves all propagate at the same speed in water. Is this true and if so what is this speed? How do temperature and salinity influence it? Keria (talk) 22:14, 2 February 2008 (UTC)

Longitudinal waves and transverse waves can travel at different velocities in the same medium. These would correspond to underwater acoustics and ocean surface waves, respectively. The speed of each is explained in underwater acoustics#Speed of sound, density and impedance and ocean surface waves#Science of waves, although I'll admit the latter is not very satisfying. Someguy1221 (talk) 22:53, 2 February 2008 (UTC)
And specifically, if you follow the last link above (which I've fixed), you'll see that the answer is no. Roughly speaking, bigger waves travel faster; tsunamis are the fastest of all. --Anonymous, 23:30 UTC, 2008-02-02.
Oh yes, forgot. As with the above, the velocity of a water wave varries with its wavelength/frequency. Someguy1221 (talk) 00:20, 3 February 2008 (UTC)
There's a hard mathematical treatment of the relationship between wave amplitude, frequence, and velocity in Dispersion (water waves). TenOfAllTrades(talk) 16:30, 3 February 2008 (UTC)
I've been to the ocean, and I can attest to the fact that waves don't all go the same speed :) —Preceding unsigned comment added by 71.196.233.110 (talk) 18:00, 3 February 2008 (UTC)

Zen monks pain suppression[edit]

I've heard several times that some trained shamans or monks can suppress the feeling of pain. The latest mention of it was in the SciFi film '[The man from earth]' (which I recommend). Is this pure fiction or has it a basis in reality? How would it work? Would it be a real suppression or 'only' a great tolerance to pain? Thank you. Keria (talk) 22:21, 2 February 2008 (UTC)

Given that Thich Quang Duc peformed self-immolation in front of a crowd and was photographed, and that a few other monks have done the same or similar...I'd say there's gotta be some truth to it. Beyond that, I have no idea. It would have to be either stopping the signals from reaching the brain or just ignoring them once they got there...but that's obvious. I suppose, if they're in a trance or whatever, that some parts of their brains have shut down (sorta like when you sleep), and if one of those parts is the part that processes pain, they won't feel it. Of course, you'll feel pain even when you're asleep if it's strong enough, so who knows how they would do that...there have been a few studys into it (I think), but I don't know where they are. Trimethylxanthine (talk) 23:17, 2 February 2008 (UTC)
Having had surgery while conscious, I can attest that medications make it possible to still feel the pain, but to not be troubled by it. Perhaps a monk would be able to transcend dental medication while getting a tooth cavity drilled out. Edison (talk) 01:42, 3 February 2008 (UTC)
Transcend dental medication... LOL. —Keenan Pepper 07:32, 3 February 2008 (UTC)

I would point out that meditation increases awareness; it does not mean going into any sort of trance or supressing anything. It also helps you to relax. I've been meditating for over thirty years, and I've never had an anaesthetic for tooth fillings or even root canal work. If you increase your awareness of the sensation of "pain", and don't fight it but relax into it (and relaxation is really the key), you become aware that it is simply a strong, even interesting, sensation. I'm certainly not insensitive to pain, and trying to suppress the sensation is exactly what not to do. (This is not medical advice.)--Shantavira|feed me 09:37, 3 February 2008 (UTC)

The concept of Qi might interest you. --Ouro (blah blah) 18:44, 3 February 2008 (UTC)
Lawrence of Arabia would hold a lighted candle under his hand without flinching. He said that it wasn't that he didn't feel the pain, but that he didn't mind the pain. It's all in the mind/attitude, apparently. -- JackofOz (talk) 01:50, 4 February 2008 (UTC)

Regulatory region vs sequence[edit]

"Regulatory region" gets more google hits than "regulatory sequence". Can I confirm a preference for regions (for merging purposes (gathering consensus on the talkpages will take months)). ----Seans Potato Business 23:14, 2 February 2008 (UTC)

I get 373 hits for "regulatory sequence" and only 254 for "regulatory region". It says 159,000 and 338,000 hits respectively on the first page, but if you actually go through the pages (repeatedly clicking on the rightmost "o"), they end after 373 and 254 respectively. I think it's a really bad idea to use Google hit counts as evidence of anything. -- BenRG (talk) 01:33, 3 February 2008 (UTC)
That's outrageous! I knew they were up to something and now I've got all the proof I need!! Thanks :) ----Seans Potato Business 01:59, 3 February 2008 (UTC)
Both are completely different concepts, and depending on the existing content, I do not think that they should be merged. Maybe you should let somebody with more biological background decide. Сасусlе 23:42, 3 February 2008 (UTC)
I already did the merge but should point out that before I came along, 'regulatory region' already redirected to 'regulatory sequence' and the alternative article was actually 'regulatory regions' (plural). Furthermore, the 'regulatory sequence' article already included 'regulatory region' as one of the synonyms. I'm looking into it now. ----Seans Potato Business 09:44, 5 February 2008 (UTC)

Physics pendulum question[edit]

What would be other examples where a pendulum would be used for timing? I already thought of a metronome and a clock, is anyone able to think of anything else? Icestorm815 (talk) 23:44, 2 February 2008 (UTC)

Surely using a pendulum as timing is always just a variation on a metronome. -mattbuck 00:33, 3 February 2008 (UTC)
Foucault's pendulum is interesting--TreeSmiler (talk) 02:27, 3 February 2008 (UTC)
The Pendulum article states that:
... in 1671, Jean Richer demonstrated that the periodicity of a pendulum was slower at Cayenne than at Paris. From this he deduced that the force of gravity was lower at Cayenne. Huygens reasoned that the centripetal force of the Earth's rotation modified the weight of the pendulum bob based on the latitude of the observer.
--hydnjo talk 04:52, 3 February 2008 (UTC)
Thanks for the ideas! Icestorm815 (talk) 16:49, 3 February 2008 (UTC)